The need to develop more effective strategies to combat neuronal degeneration has focused attention on defining the cellular-mechanisms underlying neuronal apoptosis. As Sindbis virus (SV) infection triggers neuronal apoptosis in vitro, this paradigm provides a useful model system for investigating this process. Previous studies from our laboratory reveal that oxidative stress can trigger the orchestrated events of neuronal apoptosis. These results, along with recent observations from other laboratories suggesting that the anti-apoptosis gene, bcl-2, may act as an antioxidant, cast oxidative stress induced death in a new light and suggest that if cellular defenses are inadequate to neutralize undesirable by-products of oxidative reactions, then the resultant unopposed oxidants may be a signal commonly utilized to initiate neuronal apoptosis. In preliminary studies, we have shown that: a) drugs with antioxidant capability, N-acetylcysteine (NAC) and pyrrolidinedithio-carbamate (PDTC), prevent SV-induced apoptosis in a neuroblastoma cell line, b) SV induces activation of the redox sensitive transcription factor NF-kB and this response is blocked by NAC and PDTC, and c) actinomycin-D, a selective inhibitor of host cell transcription, inhibits SV-induced apoptosis. Taken together, these results suggest that activation of a redox-sensitive host transcription factor pathway is required for SV-induced apoptosis. In this project, we propose to investigate the signalling pathways that lead to SV-induced host cell transcription and apoptosis. In particular, we intend: l) to define the spectrum of redox-sensitive transcription factors that are activated by SV infection, 2) to determine whether PDTC and NAC block SV-induced transcription factor activation by inhibiting SV-induced oxidative stress, 3) to determine whether expression of the proto-oncogene, bcl-2, a putative antioxidant, inhibits SV-induced activation of these transcription factors, and 4) to assess whether molecular manipulations of SV-activated transcription factor pathways that mimic PDTC/NAC's effects on them, also block viral- induced apoptosis.